The Drosophila population genetics laboratory will be involved in three major research projects directed towards determining the population dynamics of genetic loci exhibiting meiotic drive (excess recovery of the driven allele in the gametes) especially in relation to the possibility of using Y-chromosome drive as a means of pest population control. (1) We will attempt to increase the efficiency of pseudo-Y drive exhibited by translocation lines which couple the Y chromosome to the autosomal drive locus SD. Such lines give unisexual male progeny owing to the drive-mediated elimination of X,SD ion gametes and the concomitant lethality of aneuploid X,SD zygotes. The fitness (and hence the overall drive efficiency) of such pseudo-Y drive can be improved by increasing the segregation of Y plus SD from X plus SD ion to reduce the frequency of the wasted zygotic lethals. This can be accomplished in one of two ways: (a) by the insertion of the Y chromosomal pairing and fertility factors into the SD chromosome, or (b) by moving the SD complex out of its second chromosome milieu onto the Y chromosome. The latter project wll also enable us to investigate questions concerning the structure and dosage relationships of the several components of the SD system. (2) We will examine the dynamics of the long-term accumulation of drive suppressors in population cages where Y drive lines are competing with normal flies. Of particular interest is whether suppressors can accumulate fast enough to prevent drive-induced population extinction. We also intend to determine which parts of the Drosophila genome contribute most to drive suppression, as well as to map any major suppressors which arise. It is hoped that we an use this information to generate theoretical population genetic models which more accurately predict the fate of drive systems in natural populations. (3) We will examine natural insect populations with the hope of finding new cases of meiotic drive. Such cases, expecially if they are similar in mechanism to those already known, may help to determine both the evolutionary importance of drive and the general practicality of using it as a control system in organisms other than D. melanogaster.